#include<stdio.h>
#include "stack.h"  
// #include "headPath/stack.h" 这样就不用指定 gcc -IheadPath了
int a,b =1;

int main(void)
{
    
    push('a');
    push('b');
    push('c');
    while(!is_empty())
        putchar(pop());
    return 0;
}
